1. Field of the Invention
This invention relates to the field of adjustably-positionable supports for persons, for example of the type used by dentists to position a patient at a convenient height and inclination, and in particular to such a support wherein the patient is supported in the first instance by a wheelchair, the wheelchair being engaged by the adjustably-positionable apparatus.
2. Prior Art
Person-supporting chairs used by dentists, hairdressers and the like are well known. By electric, pneumatic or hydraulic actuating means, normally controlled by means of foot switches or the like, the dentist, dental auxiliary or other user positions the patient at an attitude most comfortable and convenient for a particular procedure to be undertaken. Dentists and dental auxiliaries normally tilt the back of the patient's chair backwards to a relatively low angle, and then raise the patient to within convenient reach.
It has been necessary heretofore in connection with patients occupying wheelchairs to move the patient out of the wheelchair and into the dentist's chair, whereupon the patient would be treated in the usual manner. This procedure can be difficult, and in order to accommodate moving patients in and out of wheelchairs and the like, various complicated and expensive suspension devices have been developed. These devices are moderately dangerous for the patient, who is vulnerable to injury if dropped or jerked about.
The present invention avoids any need to transfer a patient from the safety of the wheelchair to similar safety in the dentist's chair. The invention retains benefits equal to or greater than the dentist's chair, such as the adjustability benefits of a typical dentists' chair. The patient and wheelchair are together wheeled onto an adjustable support mechanism engaging the wheelchair and having tilt means and, preferably, vertical positioning means. This allows the patient to be wheeled onto the device, then lifted and tilted as required in order to position the patient's oral area at the correct inclination and height, but using the mobility of the wheelchair for moving the patient into place.
Wheelchair lifts are known in connection with public transportation equipment, elevators to traverse stairs and the like. In these cases, the wheelchair is wheeled onto a movable platform which can be hydraulically or electrically raised and lowered to allow the wheelchair to be wheeled on at one level and wheeled off at another. It is normally considered dangerous to allow a wheelchair-supporting device to tilt, due to the danger that the wheelchair will roll off the tilting support or that the chair will fall over. According to the invention, the wheelchair is engaged by the device, for example rolled to the back of an L-shaped support, which is then tilted to retain the wheelchair against the L, safely and securely. Due to engagement of the chair it is not readily possible to remove the chair from the device once the device is moved out of its lower-most up-right position.
In positioning an item which must be raised and also tilted, and is as large and irregularly weighted as a person in a wheelchair, substantial stability problems are encountered. When an item such as a wheelchair is positioned at a tilt and is raised high above its supporting base, relative movements, for example caused when making small corrections in position, frequently cause the support structure to wobble. This wobbling is very disturbing to the dentist as well as the patient and if resonance is involved, the wobbling can even upset the support. The present invention concerns independent height and tilt adjusting mechanisms, and when raised to the maximum and tilted, the structural arrangement, in particular the linkage driving the degree of tilt, has a varying lever arm whereby the greatest relative motion of the support structure per unit of drive motion (i.e. the minimum mechanical advantage of the drive) is achieved when the device is in its lower-most up-right stable position, and the maximum mechanical advantage (i.e., the minimum lever arm and therefore the least possibility of wobbling and lurching) is encountered at the maximum tilt.
Control of the raising/lowering and tilting functions of the invention are preferably independent for greatest versatility. Limit switches are provided to cut power to the length-extendable devices, preferably electric linear actuators, when full deflection of the actuators is reached. The limit switch technique is also used for other control functions, for example to preclude operation of the chair until the wheelchair rests against the back of its support.
The invention concerns a device especially useful in connection with institutions where a substantial number of inmates use wheelchairs. Instead of having to transport successive patients in either direction between their wheelchairs and a supportive (dentist's) chair, a user (dentist) at such an institution can simply wheel the patient into position engaging the support mechanism and otherwise proceed in a conventional manner. The "user" is not limited to a dentist or dental auxiliary, but also includes hairdressers, barbers and the like. The invention is also applicable to ophthamology, optometry, podiatry and other medical fields.